As noted, a negative sense of נָגַשׂ nagas, is the most appropriate:
Despite this, in Zechariah 10:4, נָגַשׂ is most often (50%) translated as an indeterminate "ruler" and the other half is divided among terms having either a military sense or the negative:
Appointer of tribute 1
The NET opts for "ruler" and includes a translation note:
From him will come the cornerstone,4 the wall peg,5 the battle bow, and every ruler.6 [NET2]
6 tn This is not the usual word to describe a king of Israel or Judah (such as מֶלֶךְ, melekh, or נָשִׂיא, nasiʾ), but נוֹגֵשׂ, noges, “dictator” (cf. KJV “oppressor”). The author is asserting by this choice of wording that in the messianic age God’s rule will be by force.
Essentially the translator understands the passage within the context of the Messianic age. In this inherently "positive" era, there will be a nagas who seemingly is successful in battle:
And they will be like warriors trampling the mud of the streets in battle. They will fight, for the LORD will be with them, and will defeat the enemy cavalry.7
Ignoring the negative lexicon in favor of the more neutral "ruler" may be justified if one sees the ruler as a "ruler" in the military sense (commander, leader, or officer). Translators who understand the role of the nagas in support of the LORD, can justify replacing the negative meaning with something neutral or simply emphasize the military position.
On the other hand, military success is hardly a compelling reason to discount the literal meaning. As anyone who has served in the military knows, many successful leaders were taskmasters, demanded tribute, and could accurately be labeled a tyrant or an oppressor, exactly as the lexicon states.
Additionally, another a good reason for choosing to keep the negative meaning is by considering what the ruler is not known as. As the NET observes, the ruler is not a king (מֶלֶךְ melek) or a prince (נָשִׂיא nasiy'). In the Messianic age, it is unlikely a Davidic ruler would be called a נָגַשׂ nagas. Further, Zechariah describes a future day in which the LORD will battle those who come against His people and their city:
A day of the LORD1 is about to come when your possessions2 will be divided as plunder in your midst. For I will gather all the nations against Jerusalem3 to wage war; the city will be taken, its houses plundered, and the women raped. Then half of the city will go into exile, but the remainder of the people will not be taken away.4 Then the LORD will go to battle5 and fight against those nations, just as he fought battles in ancient days.6 (Zechariah 14:1-3)
5 sn The statement the LORD will go to battle introduces the conflict known elsewhere as the “battle of Armageddon,” a battle in which the LORD delivers his people and establishes his millennial reign (cf. Joel 3:12, 15-16; Ezek 38-39; Rev 16:12-21; 19:19-21).
In the final battle, there will be opposition to the LORD. So the advent of the Messianic age is not necessarily one in which all rulers will be "good;" some may be oppressive and convince others to stay on and fight against Jerusalem. Given this uncertainity on who is truly for and against the LORD, the King James family and those who choose "oppressor" or "exactor" may be right to preserve the literal meaning.
Other NET notes:
4 tn On the NT use of the image of the cornerstone, see Luke 20:17; Eph 2:20; 1 Pet 2:6.
5 tn The metaphor of the wall peg (יָתֵד, yated), together with the others in this list, describes the remarkable change that will take place at the inauguration of God’s eschatological kingdom. Israel, formerly sheep-like, will be turned into a mighty warhorse. The peg refers to a wall hook (although frequently translated “tent peg,” but cf. ASV “nail”; TWOT 1:419) from which tools and weapons were suspended, but figuratively also to the promise of God upon which all of Israel’s hopes were hung (cf. Isa 22:15-25; Ezra 9:8).
7 tn Heb “and the riders on horses will be put to shame,” figurative for the defeat of mounted troops. The word “enemy” in the translation is supplied from context.
1 sn The eschatological day of the LORD described here (and through v. 8) is considered by many interpreters to refer to the period known as the great tribulation, a seven year time of great suffering by God’s (Jewish) people culminating in the establishing of the millennial reign of the LORD (vv. 9-21). For other OT and NT references to this aspect of the day of the LORD see Amos 9:8-15; Joel 1:15-2:11; Isa 1:24-31; 2:2-4; 4:2-6; 26:16-27:6; 33:13-24; 59:1-60:22; 65:13-25; Jer 30:7-11; 32:36-44; Ezek 20:33-44; Dan 11:40; 12:1; Matt 24:21, 29; 25:31-46; Rev 19:11-16.
2 tn Heb “your plunder.” Cf. NCV “the wealth you have taken.”
3 map For location see Map5-B1; Map6-F3; Map7-E2; Map8-F2; Map10-B3; JP1-F4; JP2-F4; JP3-F4; JP4-F4.
4 tn Heb “not be cut off from the city” (so NRSV); NAB “not be removed.”
6 tn Heb “as he fights on a day of battle” (similar NASB, NIV, NRSV).